1. Field of the Invention
The present invention relates to an image transmission apparatus in digital TV broadcasting, and more particularly, to a technique for transmitting copyright and added data by using a hidden area in digital TV broadcasting.
2. Description of the Related Art
In a digital broadcasting system, all procedures are executed with digital signals, so that high image quality can be implemented and high sound quality can be implemented in a wide range of from a lower sound level to an upper sound level. Therefore, the digital broadcasting system has been applied widely and actively to terrestrial broadcasting, satellite broadcasting, cable TV broadcasting, and the like.
The United States of America employed an 8-VSB (vestigial side band) transmission system as a standard of the terrestrial digital TV broadcasting in 1995, and test broadcasting began in the later half of 1998. South Korea also employed the 8-VSB transmission system as a standard, and the terrestrial digital TV broadcasting has been provided.
In general, the digital TV broadcasting can be performed with a high quality of image, and transmission efficiency is high in comparison to analog TV broadcasting, so that much more amount of information can be transmitted and received. In addition, recently, the United State of America employed ATSC M/H (Mobile/Handheld) broadcasting standard for the digital TV broadcasting using various mobile apparatuses such as PDAs, PMPs, and MP3 players.
In general, in digital TV broadcasting employed by ATSC (Advanced Television Systems Committee) of the United State of America, a terrestrial VSB transmission system is used. In the digital TV system, video data and a synchronization signal are separately transmitted. A receiver side needs to accurately detect a position of the synchronization signal from the video data. Since the synchronization signal has a function of identifying predefined sections of the video data, it is very important to accurately detect the position of the synchronization signal. In other words, since the synchronization signal is used as a reference of time when other components of the receiver performs signal processing, it is important to accurately detect the synchronization signal at the video data reception stage. In general, a synchronization signal pattern is inserted into the video data in the digital broadcasting signal so that the receiver side can detect the synchronization signal.
In general, in a VSB transmission scheme, a specific synchronization signal pattern is periodically inserted into a datastream (or a bitstream) so that a DTV receiver can easily detect the synchronization signal.
In this case, one datastream is configured as a sequence of data segments of 832 symbols and is divided into a synchronization signal section of 4 symbols and a data section of 828 symbols.
In addition, the synchronization signal section is a 2-level signal of ‘−1’ or ‘+1’, and the data section is an 8-level digital signal.
The transmission systems of a terrestrial digital TV broadcasting are mainly classified into two schemes. The one is the TCM (trellis coded modulation) type 8-VSB transmission system employed in the United State of America and South Korea, and the other is a COFDM (coded orthogonal frequency division multiplexing) transmission system employed in Europe.
In domestic broadcasting systems providing terrestrial digital TV broadcasting, video is compressed by using an MPEG-2 video at the Main Profile@High Level (MPEG-2MP@HL) compression method, and audio is compressed by using a Dolby-AC3 method.
As representative methods of compressing full HD (high definition) video images, there are an MPEG2MP@HL scheme used in the digital TV broadcasting and H.264 which is an Internet moving picture compression standard used for Youtube, IPTV, and the like. The full HD video image is configured with effective pixels of 1920×1080 (horizontal pixels×vertical lines). In the MPEG2MP@HL scheme and the H.264 full HD video compression method, a block is used as a minimum unit, but a slice and a macroblock is used as a basic unit. Therefore, an input image for full HD video compression needs to be 16 times of the basic unit of the slice and the macroblock. This is expressed by the following Equation.Active PixelsTotal=n×16Active LinesTotal=n×16  [Equation 1]
However, the number of pixels of the full HD image defined according to the MPEG, ATSC, and DVB standards is 1080 lines, which is not 16 times the basic unit of the slice and the macroblock. Therefore, the input full HD image is extended by using a border extender according to a method of extending 8 lines under a frame in the video encoder as illustrated in FIG. 1 in order to satisfy the condition of “16 times”.
FIGS. 1A and 1B are views illustrating screens where a border extender for full HD video compression is executed.
FIG. 1A illustrates a screen where a full HD image area is configured with 1920×1080.
FIG. 1B illustrates a screen where an extended border area is added under the full HD image area by extending the image by executing the border extender.
The MSSG (MPEG Software Simulation Group) proposes a method of repeating a final line as a reference. In a real-time encoder used for actual broadcasting, the quality of image at the reception stage can be improved by taking into consideration various digital filters used for a receiver due to complexity of hardware.
FIGS. 2A to 2D are views illustrating examples of screens where extended border areas are added to full HD images in terrestrial DTV broadcasting. In FIGS. 2A and 2B, screens where currently broadcasted terrestrial digital TV programs are received and recorded and restored are illustrated so as to show how to use the extended border area.
FIGS. 2A, 2B, 2C, and 2D are examples of screens of broadcasting systems, KBS, MBC, SBS, and EBS.
Referring to FIGS. 2A to 2D, the broadcasting systems KBS, MBC, and SBS use a border having pixel values of 0R, 0G, and 0B, and the broadcasting system EBS uses a boarder having pixel values of 131R, 131G, and 131B. The values 131R, 131G, and 131B of the EBS are pixels values having intermediate brightness by taking into consideration gamma values of the receiver. In addition, as a peculiar point, in the case of the SBS, a black line exists in the upper portion of the frame.
However, a technique of transmitting copyright or data of contents to the extended border area as a hidden area in a DTV image screen has not been proposed in the related art.
Korean Patent Application Publication No. 10-2013-0098027 is provided as a cited document.